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The question has two errors so first let’s get them out of the way.

The first one is a category error, in that cold infection is caused by a replication capable entity, the rhinovirus (the cold virus), while allergies tend to be largely caused by replication incapable entities (so-called “allergens“) such as excretory products of dust mites, cockroaches, cat sebaceous glands, etc. Thus, when considering immune responses against cold viruses versus those against “allergens”, there is a difference in kind in that viruses are subject to evolutionary selection pressures, namely anti-viral immunity, while this consideration is largely moot for “allergens”. This category difference not only mandates different prophylactic and therapeutic approaches for cold infection versus allergies but also implies that effective immune responses in these two instances are likely to be subject to different pressures.

The second error concerns the interpretation that allergies are products of an overactive immune system. While this may have been believed at one time, an abundance of subsequent research suggests that allergies are rather manifestations of dysregulation, not overactivation, of the immune system (1, 2, 3).

The connection between growing up on farms and incidence of cold infection appears to be indirect. On the one hand, early life exposure to farms correlates with lower incidence of asthma, hay fever and other allergies (4, 5, 6, 7, 8, 9, 10, 11, 12). On the other hand, cold infections tend to be more frequent, more severe and more long lasting in asthmatics compared to non-asthmatics (13, 14, 15).

It is well appreciated that persistent allergies have the capacity for extensive airway remodeling (16, 17). Airway remodeling refers to semi-permanent to permanent, long-lasting structural and functional changes in the upper respiratory tract that increase airflow obstruction and importantly for airway homeostasis, increased secretion of certain inflammatory mediators such as TGF-beta (18, 19). In turn, such changes render an allergic individual more susceptible to cold infections.

Thus, growing up on farms —> less likely to develop allergies —> less likelihood of airway remodeling and other immune dysregulation mediated tissue pathologies—> apparent lower susceptibility to cold infections.

1. Dysregulation of Complement System and CD4+ T Cell Activation Pathways Implicated in Allergic Response
2. The role of epigenetic dysregulation in the epidemic of allergic disease
3. Immune dysregulation in asthma
4. Austrian children living on a farm have less hay fever, asthma and allergic sensitization
5. Reduced risk of hay fever and asthma among children of farmers
6. Farm environment in childhood prevents the development of allergies
7. Relative Scarcity of Asthma and Atopy among Rural Adolescents Raised on a Farm
8. Exposure to farming in early life and development of asthma and allergy: a cross-sectional survey
9. Elsevier
10. Farm exposure in utero may protect against asthma, hay fever and eczema
11. Elsevier
12. Page on nature.com
13. Elsevier
14. Viral Infections, Cytokine Dysregulation and the Origins of… : The Pediatric Infectious Disease Journal
15. Page on nih.gov
16. Regulation of Activin A Expression in Mast Cells and Asthma: Its Effect on the Proliferation of Human Airway Smooth Muscle Cells
17. Increased Vascularity of the Bronchial Mucosa in Mild Asthma
18. Transforming Growth Factor- β 1 in Asthma
19. Eosinophil-associated TGF- β1 mRNA Expression and Airways Fibrosis in Bronchial Asthma

Are people who grew up in farms less prone to cold infections?

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